Question

two concentric circles are of radii 5cm and 3cm. length of the chord of the larger circle, (in cm), which touches the smaller circle is.?

Answer 1

Let the radius of the bigger circle be 'R' and the radius of the smaller circle be 'r'.
It is given that R=5cm=OB and r=3cm=OD and AB is the chord whose length we have to find.
AD=BD and OD⊥AB(radius is perpendicular to a chord and it divides the chord into two equal parts)
therefore, ΔODB is a right angled triangle
where, OD²+BD²=OB²
            (3)²+BD²=(5)²
             9+BD²=25
             BD²=25-9
             BD²=16
             BD=4cm
       Since AD=BD=4cm
       therefore, AB=AD+BD
                       AB=4+4
                       AB=8cm

Answer 2

hope it helps you!!!!!!!!